const a1 = document.getElementById("a1"); //HTMLElement元素对象
// console.log(a1.href);

const a2 = document.getElementById("a1") as HTMLAnchorElement;
console.log(a2.href);

const d1 = document.getElementById("d1");
const d2 = <HTMLDivElement>document.getElementById("d1");
console.log(d2.title);
